Speech enhancement based on the general transfer function GSC and postfiltering

In speech enhancement applications, microphone array postfiltering allows additional reduction of noise components at a beamformer output. Among microphone array structures, the recently proposed general transfer function generalized sidelobe canceller (TF-GSC) has shown impressive noise reduction abilities in a directional noise field, while still maintaining low speech distortion. However, in a diffused noise field, less significant noise reduction is obtainable. The performance is even further degraded when the noise is nonstationary. We present three postfiltering methods for improving the performance of microphone arrays. Two of them are based on single-channel speech enhancers and make use of recently proposed algorithms concatenated to the beamformer output. The third is a multichannel speech enhancer which exploits noise-only components constructed within the TF-GSC structure. An experimental study, which consists of both objective and subjective evaluation in various noise fields, demonstrates the advantage of the multi-channel postfiltering compared to single-channel techniques.